In a developing device of an electrophotographic image forming apparatus such as a copying machine or a printer, there is a device to supply toner to the developing device by an attachable and detachable toner cartridge. The model number of the toner cartridge varies according to, for example, the destination or the color of the toner. In order to prevent a toner cartridge having an improper model number from being used for an image forming apparatus, there is a device in which nested concave and convex parts to discriminate the model number are provided on a body of the image forming apparatus and the outer periphery of a toner container of the toner cartridge. If the toner cartridge has the proper model number, the concave and convex parts of the body of the image forming apparatus and the outer periphery of the toner container are fitted to each other, and the toner cartridge is mounted in the image forming apparatus.
However, in order to provide the concave and convex parts for discriminating the model number on the outer periphery of the toner container, a mold for forming the toner container must be prepared for each model number, and there is a fear that cost reduction is prevented.